South Korea's foreign ministry called in a senior Japanese diplomat on Sunday and filed a strong protest after Tokyo sent a central government official to a local event aimed at bolstering the country's claims to the South's easternmost islets of Dokdo.

Lee Sang-deok, director-general in charge of Northeast Asia affairs at the foreign ministry, filed the protest after summoning Hisashi Michigami, a senior minister at Japan's Embassy in Seoul, the ministry said. Lee also conveyed a verbal note that Japan's territorial claims to Dokdo are nonsense and amount to denying history, it said.

Lee also told the Japanese diplomat that relations between the two countries will "plunge deeper into the quagmire" if Japan keeps laying claims to the East Sea islets and warned that all responsibility for the consequence rests with Japan, according to the ministry.

On Saturday, Japan's Shimane Prefecture held a ceremony to promote its claims to Dokdo with a vice minister-level official and national legislators in attendance. The regional government claims Dokdo, which it calls Takeshima, falls under its jurisdiction, and designated Feb. 22 as Takeshima Day in 2006.

The ceremony came just two days after Japan's Chief Cabinet Secretary Yoshihide Suga suggested that Tokyo could reconsider a 1993 apology for its sexual enslavement of Korean women during World War II. The apology is known as the Kono statement as it was issued by then-Chief Cabinet Secretary Yohei Kono.

Later in the day, the ministry released an English-language video promoting South Korea's sovereignty over Dokdo on its website. The website also includes a link to an animation about the sexual slavery that drew wide acclaim at an international animation festival in France.

Relations between Seoul and Tokyo have been tense due to Japan's refusal to address long-running grievances over the sexual slavery and other atrocities committed during its 1910-45 colonial rule of Korea and its repeated claims to Dokdo.

Their ties soured further after Abe paid respects late last year at a war shrine that honors Japan's war dead, including 14 Class A war criminals. Abe was the first Japanese prime minister to visit the shrine in more than seven years.

South Korea rejects Japan's claim to Dokdo because the country regained its independence from Japanese colonial rule and reclaimed sovereignty over its territories, including Dokdo and many other islands around the Korean Peninsula. South Korea keeps a small police detachment on the islets. (Yonhap)